Reciprocating mechanisms



AugQ'N, 1970 o. F. MOWBRAY 3,523,459

RECIPROCATING MECHANISMS Filefi Sept. 13, 1968 NVE TOR Y m g ATTORNEYS United States Patent Office 3,523,459 Patented Aug. 11, 1970 US. Cl. 7455 2 Claims ABSTRACT OF THE DISCLOSURE A reciprocating mechanism including a tappet which carries a roller, a cam for imparting movement to the tappet and the tappet being provided with flank portions which extend adjacent the side faces of the cam thereby to prevent angular movement of the tappet.

This invention relates to reciprocating mechanisms of the kind comprising in combination, a tappet and a rotary cam for imparting movement to the tappet, the tappet incorporating a roller which bears upon the surface of the cam.

The object of the invention is to provide such a mechanism in a simple and convenient form.

According to the invention in a mechanism of the kind specified the tappet is provided with flank portions disposed on opposite sides thereof and which can bear against the opposite side surfaces respectively of the cam to prevent angular movement of the tappet.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a fuel injection pump incorporating the invention,

FIG. 2 is a section on the line 2-2 of FIIG. 1.

One example of a reciprocating mechanism in accordance with the invention will now be described as applied to a tappet and cam combination such as is found in a fuel injection pump for supplying fuel to an internal combustion engine. I

At the inner end of the bore is an outlet 13 incorporating a spring loaded non return delivery valve 14 and adapted for connection to an injection nozzle associated with an engine cylinder. Moreover, intermediate the ends of the bore is an inlet port 15 in communication with an annular recess 16 in the body part and to which fuel is fed by a feed pump or other convenient means. The inlet port 15 is so positioned in the bore that it will be uncovered by the inner end of the plunger 12 when the latter is at the outward limit of its travel thus allowing fuel to enter the pumping chamber from the annular recess 16. During the inward movement of the plunger the inlet port 15 will be covered and fuel will be delivered to the outlet 13 and hence to the engine cylinder by way of the delivery valve 14. In the periphery of the plunger and extending from its inner end is a helical groove 17 which as the plunger is moved inwardly, and after the inlet port 15 has been covered by the end of the plunger, reopens the port to spill any fuel remaining in the pumping chamber to the annular recess 16 at the same time terminating the delivery of fuel to the engine cylinder. The angular setting of the plunger 12 relative to the barrel 11 thus determines the point during the inward movement of the plunger when fuel is spilled.

Surrounding the portion of the barrel remote from the outlet is a hollow sleeve 19 having a pair of longitudinal slots 20 extending inwardly from the outer end and engaging with radial lugs 21 on the plunger. The arrangement is such that longitudinal movement imparted to the plunger will not be transmitted to the sleeve whereas angular movement of the latter will be imparted to the plunger.

Formed on the outer periphery of the sleeve 19 are teeth which engage with a toothed fuel control rod 22 mounted for axial movement transversely relative to the plunger axis, in the body part.

On the outer end of the plunger is a spring abutment collar 24 between which and a washer 25 bearing on an internal shoulder in the body part is a coiled compression spring 26 which urges the plunger outwardly. The collar 24 is located within a cam follower 27 having a roller 28 adapted to coact with a cam 29 rotatable by the engine with which the pump is associated.

With this construction it is essential that the tappet or cam follower 27 should not move angularly within the body part 10 and it has been the practice to provide a groove in the peripheral surface of the follower and to provide a peg or similar member in the body part which co-operates with the groove to prevent angular movement of the tappet. Such an arrangement has however a number of disadvantages which the arrangement to be described overcomes.

The peg and the associated groove are omitted and the follower 27 is provided with flank portions 30 which extends downwardly beyond the roller 28 on opposite sides of the cam 29. Moreover, the ifank portions extend circumferentially about the shaft 31 supporting the cam on opposite sides of the centre line as defined by the axis of the plunger 12. Moreover, the radius of the shaft 31 is smaller than the minimum radius of the cam 29 so that the latter has continuous side surfaces. The aforesaid flank portions 30 of the follower co-operate with the side surfaces of the cam to prevent angular movement of the follower.

Conveniently and as shown, the minimum radius of the cam 29 is so chosen that the end faces of the aforesaid flank portions 30 bear upon the shaft 31 when the plunger is at its outermost position. In this manner the roller is removed from the cam surface and more eflicient lubrication of the co-operating surfaces of the cam and roller and the co-operating surfaces of the roller and follower can be efliected.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A reciprocating mechanism comprising in combination, a hollow body part, a cylindrical bore mounted in the body part, a cylindrical tappet slidable within said bore, a rotary shaft mounted within the body part, a roller mounted on the tappet, a cam mounted upon the shaft and having side surfaces and a cam surface with which the roller co-operates to effect movement of the tappet, flank portions disposed on opposite sides of the tappet and which bear against the opposite side surfaces respectively of the cam to prevent angular movement of the tappet.

3 4 2. A mechanism as claimed in claim 1 in which said 1,534,509 4/1925 Falwell 12390 flank portions bear upon said shaft to remove said roller 2,192,913 3/1940 Huber 123-90 from the cam surface during the dwell period of the 2,948,159 8/1960 Wirsching 7455 cam thereby to facilitate lubrication of the co-operating 3,101,077 8/1963 Engle 7455 surfaces of the cam and roller and the roller and tappet. 5 3,267,919 8/1966 Wortman 7455 3,108,580 10/1963 Crane 74-55 References Cited UNITED STATES PATENTS WESLEY S. RATLIFF, 111., Primary Examlner 1,340,717 5/1920 Holle 12390 U.S. Cl. X.R.

1,345,942 7/1920 McCain 123- 90 10 123- 90 

